(a) Field of the Invention
The invention relates to a barcode scanner, and more particularly, to a barcode scanner capable of obtaining an effect of at least two projecting light sources using one set of laser emitter and collimator along with at least one set of beam splitter and reflector, so as to have the scanning light beams distribute evenly as well as saving production cost and material.
(b) Description of the Prior Art
FIG. 6 shows a conventional schematic view of a barcode scanner 1 having a laser emitter as the light source thereof. The structure at least comprises a laser emitter a, a collimator b (generally a piano-convex column lens that is located horizontally for converting laser light beams as strip-shaped light beams), a light condensing lens c and a linear light receiver d (may be a linear CCD sensor or a linear CMOS sensor), and the laser light source a and the collimator b are disposed at one lateral side of the light condensing lens c. After the light beams emitted from the laser emitter a are converted into strip-shaped scanning light beams after passing through the collimator b, the scanning light beams are then projected in a form of strip-shaped onto a barcode e, and the reflected images of the scanning light beams at the barcode e are focused at the linear light receiver d through the light condensing lens c. Referring to FIG. 7, the light intensity distribution at the receiving plane of the linear light receiver displays a curved pattern. The strongest light intensity thereof exists at the center of the linear light receiver d (as indicated by the centerline of the curve in FIG. 7); whereas the light intensity gets weaker as approaching the lateral sides of the linear light receiver d (the lateral side distant from the center of the linear receiver are indicated by the dotted lines in FIG. 7); that is, the reflected light beams thereof are unevenly reflected upon the receiving plane of the long linear light receiver, and a shortcoming is thus brought about for that the image information cannot be easily read by a rear-end circuit thereof.
In order to overcome the shortcoming of the aforesaid prior structure 1 described in FIG. 6, industrialists have later developed another prior structure 2 as shown in FIG. 8, wherein a laser emitter a and a collimator b are laterally disposed at each side of both sides of the light condensing lens c, so as to project and overlap light beams from two light sources onto a barcode e. The light intensity distribution of the reflected light beams at the receiving plane of the linear light receiver d displays a plateau curved line as shown in FIG. 9 (the solid line formed by the dotted lines of the overlapping light beams). Through this design, even if the light range of the projecting area is broadened, the light intensity at the receiving plane of the linear light receiver d remains quite even for increasing the light intensity reflected at the lateral sides of the linear light receiver d for better reading. Nevertheless, the light intensity at the two lateral sides of the receiving plane of the linear light receiver d somewhat accounts as insufficient (the dotted lines at the sides as shown in FIG. 9), and therefore this prior structure needs at least two sets of laser emitters and collimators that subsequently increase the production cost and material thereof; it is necessary to improve such prior art.